Uticaj vlažnosti na fizičke osobine i NR životnu sposobnost semena soje / Modulus of elasticity changes depending on soybean seed moisture

Physical and mechanical properties of seeds are essential for the design of equipment for transport, harvesting, drying and finishing. These properties are dependent on many factors such as seed size, shape and moisture content. In addition, knowledge of mechanical properties is essential for the rational design of processing and optimization process. For the study of physical and mechanical properties of soybean seed samples, two varieties were chosen , the Sava and the Balkans, which differ greatly in their varietal characteristics. Samples were taken at different stages of ripening, and their moisture content ranged from 8.1% to 21.5%. Investigated physical properties of density, porosity and bulk mass decrease with increasing moisture content in the seed, while the physical properties of volume, the static angle of filling and dynamic angle of filling and coefficient of friction increase with increasing moisture content of seeds. Dispersion analysis showed that there is a significant effect of seed moisture on individual seed physical properties. This dependence are presented graphically, and some mathematical models are determined that define these dependencies. As one of indicators of mechanical properties of seeds was used module of elasticity. According to Burubai et al. (2008) it is a measure of the seeds strength (stiffness). Strength test pressure on the seeds was carried out with a special device, with the direction of the load in the direction of the third dimension (thickness). The parameters that are measured at that moment are the force at which the destruction of seeds and seed strains are developed. Using the module of elasticity as an indicator of mechanical properties of soybean seeds, it was concluded that moisture content affects the mechanical properties of seeds. Dispersion analysis showed that there was a significant effect of seed moisture on the module of elasticity change. For all test samples modules of elasticity were calculated, corresponding diagrams were drawn and the math dependent changes, depending on the module of elasticity in relation to the change in seed moisture were given. The values of the module of elasticity decreases according to seed moisture content , for the Balkan variety from 32.53 to 6.58 N/mm2, and for the Sava variety from 22.19 to 5.24 N/mm2. This shows that the Sava variety seed is more elastic at low moisture content from the Balkan variety seed, but if the seed moisture content is above 17% these features are equal. Mechanical strength of soybean seed layer decreases with increasing moisture content in seeds. This could be due to the fact that higher moisture content causes the softening of cellulose fiber and seed becomes vulnerable to destruction. This is consistent with the results of Konak et al. (2002), B&auml;umler et al. (2006), Burubai et al. (2008). &Ouml;zarslen (2002) and Konak et al. (2002) report similar reduction in resistance to mechanical damages with increasing moisture content in cotton seed and others. Vigor tests determined the correlation of mechanical properties of the soybean seed<br /> and the quality traits such as energy of germination and germination. It is also presented the interdependence of certain physical and mechanical properties. A large number of the analyzed physical properties depending on the moisture content and the possibility of varieties, enable better introducing the possibilities of mechanical and technological operations with the soybean seed. It also indicates that there are some differences for the different varieties which is also useful for evaluating properties of seeds of different varieties.